Single Particle Thermal Detection in Superconducting Rhenium

Single-particle thermal detection of alpha-particles and gamma-rays in small composite bolometers with superconducting rhenium acting as absorber is successfully demonstrated. It is shown that, at temperatures below 100 mK, the particle energy is quickly thermalized and the effective heat capacitance of the rhenium is slightly higher than the Debye contribution but less than 1% of the electronic contribution of a metal in the normal state